1. Field of the Invention
The present invention relates to medical guide wire and a method of making the same in which a stainless steel wire is subjected to a series of mechanical procedures, and thereafter heat treated at low temperature within a predetermined temperature range in order to improve a mechanical strength characteristic of the core wire.
2. Description of Related Art
In general, a medical guide wire (referred to simply as a guide wire) is thinned so that the guide wire is inserted into a somatic vasculature. With the thinned wire in mind, it is necessary to impart mechanical requirements to the guide wire with safety measures secured for a human body. For this purpose, various types of contrivances have been introduced.
In Japanese Laid-open Patent Application No. 2003-342696 (referred to as first reference), the first reference discloses mechanical procedures and heat treatment in low temperature with the use of a high silicic stainless steel (Si: 3.0%-5.0% by weight) as a core wire. The first reference uses various heat treatments for the purpose of providing the core wire with a high tensile strength.
In Japanese Patent Application Publication No. 2000-512691 (referred to as second reference), the second reference uses an elastic shape-memory alloy to improve a product quality by undergoing certain types of mechanical procedure.
In Japanese Laid-open Patent Application No. 2005-14040 (referred to as third reference), the third reference discloses a thinned wire which is divided into several regions, each of which is twisted and heat treated in varying degrees for the purpose of improving a product quality.
With the above three references in mind, an austenitic stainless steel wire is used as a material of the core wire in the field of the related art.
However, none of the references reflects on following technological idea in producing and manufacturing the guide wire.
Upon imparting mechanical procedures to the core wire in order to satisfy physical properties needed for the guide wire, the stainless steel wire is deeply drawn as a highly wrought-out procedure. Upon providing the stainless steel wire with the mechanical procedures, observed is a thermal influence on the tensile strength characteristic of the core wire.
Considering a relationship between the mechanical procedures and the heat treatment in low temperature each time when the stainless steel wire is subjected to manufacturing procedures characteristic of the guide wire, accumulated are the procedures effective in increasing the tensile strength of the core wire in order to produce the guide wire with an increased tensile strength.
Therefore, the present invention has been made with the above drawbacks in mind, it is a main object of the invention to provide a medical guide wire and a method of making the same which enables an operator to use safely by attaining the most preferable tensile strength characteristic of the core wire in relation to mechanical procedures, to which the core wire is subjected, while considering the thermal influence on the tensile strength of the core wire when the austenitic stainless steel wire is deeply drawn as a highly wrought-out procedure upon forming the core wire.